The present invention relates to block copolymers of polyarylene sulfide, such as polyphenylene sulfide, chemically combined with blocks of polyetherimide or polydiorganosiloxane. The block copolymers can be used as high performance injection moldable thermoplastics. In addition, the block copolymers can be used as compatibilizers for blends of polyarylene sulfide with other polymers such as polyetherimides and polydiorganosiloxanes.
Prior to the present invention, it was generally known that polyarylene sulfides, such as polyphenylene sulfide, were highly crystalline engineering thermoplastics (MP 285.degree. C.). Because of their crystallinity, polyarylene sulfides are extremely resistent to aggressive solvents, including dipolar solvents and chlorinated hydrocarbons. However, because of their low glass transition temperatures, for example polyphenylene sulfide has a T.sub.g of 85.degree. C., these potentially valuable thermoplastics shown relatively low heat deflection temperature (HDT of 105.degree. C.) without any reinforcement, such as fillers and fibers. Block copolymers of polyphenylene sulfide, for example polyphenylene sulfide-polyamide block polymers are shown by Macromol. Chem., 184 1861 (1983) and Polym. Bulletin, 6, 477 (1982).
The present invention is based on our discovery that polyarylene sulfide block copolymers, such as polyarylene sulfide-polyimide block copolymers and polyarylene sulfide-polydiorganosiloxane block copolymers can be made having significantly improved heat distortion temperature compared to polyarylene sulfide homopolymer.